Plant shelters are used to protect young plants against early frost, damaging wind, unseasonably cool weather, heavy rain, hail, excessive sunlight, and insects and other pests. Heat and moisture are also conserved within the shelters to provide an environment that promotes seed germination and plant growth. Plant shelters thus allow for earlier plantings and can significantly extend growing seasons, especially in colder climates.
There are many designs of plant shelters described in the prior art. For example, Easterling U.S. Pat. No. 718,109, Scott U.S. Pat. No. 912,184, and Campbell U.S. Pat. No. 1,112,052 each describe a plant protective cover with a wire support frame and a canvas or cloth cover. Formed paper and thin plastic caps with and without fixed openings are other known designs. Other plant protectors are described in U.S. Pat. No. 3,812,616, which also includes a rigid frame and in this case a transparent, flexible plastic cover, and British Patent Specification No. 714,784, which describes a cover made of a semi-rigid polyvinyl with stiffening ribs.
The prior art further includes various means for controlling ventilation in plant shelters. U.S. Pat. No. 3,214,865 to Rosenvold et al, for example, discloses a plant shelter formed from a transparent or translucent plastic material that is perforated to form a series of knockout sections from which ventilation openings are formed. U.S. Pat. No. 1,814,339 to Sato discloses a glass plant shelter that controls admission of air with an adjustable cap covering an opening and in which light is controlled by a rotatable corrugated glass side intended to diffuse light and heat.
Our own prior invention of an improved plant shelter, as described in our U.S. Pat. No. 5,398,443, compromises a dome-shaped translucent body or shell molded from a resin material, having openings or windows formed in a peripheral wall of the shell, and a cover made of transparent flexible film. The cover alternately can overlay the windows to protect the interior from wind, or rolled up at its open end to expose some or all of the windowed areas to adjust the amount of air admitted through the windows.